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<h1><a name="SECTION0018700000000000000000">
16.7 <tt class="module">termios</tt> --
         POSIX style tty control</a>
</h1>

<p>
<a name="module-termios"></a>  
<p class="availability">Availability: <span
 class="platform">Unix</span>.</p>

<p>
<a id='l2h-3543' xml:id='l2h-3543'></a><a id='l2h-3544' xml:id='l2h-3544'></a>
<p>
This module provides an interface to the POSIX calls for tty I/O
control.  For a complete description of these calls, see the POSIX or
<span class="Unix">Unix</span> manual pages.  It is only available for those <span class="Unix">Unix</span> versions
that support POSIX <em>termios</em> style tty I/O control (and then
only if configured at installation time).

<p>
All functions in this module take a file descriptor <var>fd</var> as their
first argument.  This can be an integer file descriptor, such as
returned by <code>sys.stdin.fileno()</code>, or a file object, such as
<code>sys.stdin</code> itself.

<p>
This module also defines all the constants needed to work with the
functions provided here; these have the same name as their
counterparts in C.  Please refer to your system documentation for more
information on using these terminal control interfaces.

<p>
The module defines the following functions:

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3545' xml:id='l2h-3545' class="function">tcgetattr</tt></b>(</nobr></td>
  <td><var>fd</var>)</td></tr></table></dt>
<dd>
Return a list containing the tty attributes for file descriptor
<var>fd</var>, as follows: <code>[</code><var>iflag</var>, <var>oflag</var>, <var>cflag</var>,
<var>lflag</var>, <var>ispeed</var>, <var>ospeed</var>, <var>cc</var><code>]</code> where
<var>cc</var> is a list of the tty special characters (each a string of
length 1, except the items with indices <tt class="constant">VMIN</tt> and
<tt class="constant">VTIME</tt>, which are integers when these fields are
defined).  The interpretation of the flags and the speeds as well as
the indexing in the <var>cc</var> array must be done using the symbolic
constants defined in the <tt class="module">termios</tt>
module.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3546' xml:id='l2h-3546' class="function">tcsetattr</tt></b>(</nobr></td>
  <td><var>fd, when, attributes</var>)</td></tr></table></dt>
<dd>
Set the tty attributes for file descriptor <var>fd</var> from the
<var>attributes</var>, which is a list like the one returned by
<tt class="function">tcgetattr()</tt>.  The <var>when</var> argument determines when the
attributes are changed: <tt class="constant">TCSANOW</tt> to change immediately,
<tt class="constant">TCSADRAIN</tt> to change after transmitting all queued output,
or <tt class="constant">TCSAFLUSH</tt> to change after transmitting all queued
output and discarding all queued input.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3547' xml:id='l2h-3547' class="function">tcsendbreak</tt></b>(</nobr></td>
  <td><var>fd, duration</var>)</td></tr></table></dt>
<dd>
Send a break on file descriptor <var>fd</var>.  A zero <var>duration</var> sends
a break for 0.25-0.5 seconds; a nonzero <var>duration</var> has a system
dependent meaning.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3548' xml:id='l2h-3548' class="function">tcdrain</tt></b>(</nobr></td>
  <td><var>fd</var>)</td></tr></table></dt>
<dd>
Wait until all output written to file descriptor <var>fd</var> has been
transmitted.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3549' xml:id='l2h-3549' class="function">tcflush</tt></b>(</nobr></td>
  <td><var>fd, queue</var>)</td></tr></table></dt>
<dd>
Discard queued data on file descriptor <var>fd</var>.  The <var>queue</var>
selector specifies which queue: <tt class="constant">TCIFLUSH</tt> for the input
queue, <tt class="constant">TCOFLUSH</tt> for the output queue, or
<tt class="constant">TCIOFLUSH</tt> for both queues.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3550' xml:id='l2h-3550' class="function">tcflow</tt></b>(</nobr></td>
  <td><var>fd, action</var>)</td></tr></table></dt>
<dd>
Suspend or resume input or output on file descriptor <var>fd</var>.  The
<var>action</var> argument can be <tt class="constant">TCOOFF</tt> to suspend output,
<tt class="constant">TCOON</tt> to restart output, <tt class="constant">TCIOFF</tt> to suspend
input, or <tt class="constant">TCION</tt> to restart input.
</dl>

<p>
<div class="seealso">
  <p class="heading">See Also:</p>

  <dl compact="compact" class="seemodule">
    <dt>Module <b><tt class="module"><a href="module-tty.html">tty</a></tt>:</b>
    <dd>Convenience functions for common terminal control
                  operations.
  </dl>
</div>

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